Scum removing apparatus

ABSTRACT

A spraying means is arranged on the scum-flowing wall surface side of wall surfaces forming a scum inlet of a scum discharging mechanism. The spraying means sprays pressured water upward along the wall surface on the scum-flowing side from when a part of the scum inlet is submerged in water until the scum begins to flow into the scum inlet. As a result, even large lumps of scum exceeding 10 cm in thickness (diameter) may be lead smoothly into a pipe by the pressured water, and the amount of discharged water accompanying scum discharge may be reduced to 1/20 to 1/30 than by a conventional scum removing apparatus.

TECHNICAL FIELD

The present invention relates to a scum removing apparatus for removingscum generated at a water treatment plant such as a settling basin at asewage-treatment plant, for example. More specifically, it relates to anapparatus which can improve scum mobility so as to efficiently dischargescum.

BACKGROUND ART

Conventionally, scum generated on the water surface of a settling basinis removed by a scum removing apparatus provided on the downstream sideof the settling basin. As shown in FIG. 4 of Japanese Patent ApplicationPublication Laid-open No. Hei 9-19682, for example, a scum removingapparatus, which includes a tubular scum discharging mechanismconstituted by a pipe having an axial center direction parallel to thewater surface, including a slender opening in the axial center direction(longitudinal direction), and the pipe can rotate with the axis as acenter, wherein that pipe is rotated at the time of discharging scumsuch that a part of the opening is positioned below water so as tointroduce the scum into the pipe from the opening and discharge it, iswell-known as such a scum removing apparatus. In addition, as disclosedin FIG. 1 of Japanese Patent Application Publication Laid-open No. Hoi9-19682 and Japanese Patent Application Publication Laid-open No.2000-202436, a scum removing apparatus, which is constituted by a troughincluding a vertically moving inflow floodgate, wherein the top end ofthe inflow floodgate of the trough is positioned below water at the timeof discharging scum so as to introduce the scum into the trough via theinflow floodgate and discharge it, is also well-known.

However, the conventional scum removing apparatuses have shortcomings inthat while scum near the opening and the inflow floodgate flows into thetrough immediately after the pipe opening and the trough inflowfloodgate are positioned below water, marginal scum flows into the pipeand trough thereafter together with a large quantity of water, requiringa long time for removing all of the scum, and thereby requiring a largequantity of water for removing the scum as a result.

More specifically, there are shortcomings in that since the scumgenerating and floating on the water surface takes on a single largeplate shape with a constant thickness, hardness, and adherence(adhesion), a side of that plate-shaped scum adheres to the pipe and thetrough and other sides respectively adhere to basin walls before thepipe or the trough operate. Therefore, while a part of the scum near thepipe and the inflow floodgate (trough) flows into the pipe via theopening and the inflow floodgate in sync with the operation of the pipeand the inflow floodgate, it is easy for only water to flow into thepipe and the trough thereafter, not allowing all of the scum to beremoved in a short period of time. Moreover, when a large amount ofwater has flowed into the pipe and the trough, there is a shortcoming inthat processing load of the scum processing equipment increasesthereafter.

Furthermore, as disclosed in Japanese Patent Application PublicationLaid-open No. Hei 9-276860, for example, the conventional scum removingapparatus also sprays pressured water at an oblique angle on top of thescum in order to provide locomotive faculty to move the scum toward thepipe or trough side in sync with movement of the pipe opening to belowwater or in sync with movement of the trough inflow floodgate to belowwater. However, the conventional scum discharging method of moving scumusing only the flow of water has shortcomings in that electric power isconsumed wastefully and power cost increases since only water flows intothe pipe and the trough, this inflowing water is sent back to thesettling basin, and the sent-back water is then pumped back up to thewater treatment plant.

The applicant has already provided a scum removing apparatus in JapanesePatent No. 3943551 to solve the above-given shortcomings. The scumremoving apparatus according to this patent (hereafter referred to as‘patent apparatus’) allows the scum in the basin to smoothly flow into ascum inlet and effectively discharge the scum by smooth transfer of allof the scum.

In other words, the patent apparatus is a scum removing apparatus, whichtransfers generated scum on a current to the scum discharging mechanismside, and submerges a part of the scum inlet of the scum dischargingmechanism under water at the time of discharging scum so as to removethe generated scum. The scum removing apparatus is characterized in thatit is provided on the scum-flowing wall surface side of wall surfacesforming the scum inlet of the scum discharging mechanism, and a sprayingmeans for spraying, for example, fluid (air) made of compressed airupward is provided along the wall surface.

Moreover, the patent apparatus is characterized in that it is alsoprovided with a spraying means on the basin wall side in the water nearthe basin wall further upstream than the position at which the scumdischarging mechanism is provided, wherein the spraying means sprays airupward along the basin wall. In addition, the patent apparatus ischaracterized in that it is provided with a water spraying means, whichis provided further upstream than the position at which the scumdischarging mechanism is provided, wherein the water spraying meanssprays water obliquely downward on the scum discharging mechanism sideto transfer the scum to the scum discharging mechanism side by thespraying pressure of the water.

The patent apparatus with the above configuration allows rapid dischargeof scum since the scum may easily flow into the scum inlet and transferof all of the scum can be performed smoothly. As a result, the patentapparatus may reduce amount of water flow accompanying scum discharge to1/20 to 1/30 than by the conventional scum removing apparatus. As such,since the amount of water accompanying the scum to be discharged is farless than in the past, the patent apparatus has merits of reduction inequipment expenses for post-processing equipment such as a pressureflotation device, and reduction in power consumption of a lifting pump,thereby allowing contribution to energy conservation.

A verification test conducted at an actual certain sewage plant usingthe patent apparatus will be described. The scum removing apparatusprovided with a tubular scum discharging mechanism used in thisverification test has a 5 m-long pipe opening. When scum has grown to athickness of 7 to 10 cm and to a length of 5 m further upstream from thepipe, the scum may be completely discharged by submerging a part of thepipe opening for 5 to 7 minutes. Moreover, in a verification test atanother sewage plant, complete removal of scum by submerging a part ofthe pipe opening for 5 minutes every 24 hours and 5 minutes every 36hours has been confirmed. As a result, the patent apparatus is given thenickname ‘Once-a-week boy’ since submerging a part of the pipe openingfor approximately 10 minutes just once a week is sufficient, and hasbeen introduced in the ‘Special Issue of Monthly Journal of Sewerage (P.71)’ issued on Feb. 28, 2006.

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, when large lumps of scum exceeding 10 cm in diameter exist onthe scum inlet side of the patent apparatus, the scum cannot be raisedto the edge of the scum inlet by the force of air even if fluid of airis sprayed upward, and therefore the scum cannot flow into the pipesmoothly, becoming a possible obstacle in discharging scum.

Such large lumps of scum easily generate particularly during heavy rainand in the case of combined sewage where sewage water and rain watercollect in the same pipe and flow into the sewage plant. Moreover, suchlarge lumps of scum result from sludge, which contains oil and fatcontent included in sewage, adhering to the sewage piping inner surfaceand growing there to form into an oil ball, or formed by organic matterin the sludge remaining in an anaerobic condition. Such scum thenseparates from the sewage piping inner surface due to water pressure orcurrent during heavy rain and drifts into the sewage plant in largelumps.

Since aside from during heavy rain, the patent apparatus normally doesnot have any large lumps of scum exceeding 10 cm in diameter (thickness)on the scum inlet side, it can make the scum flow smoothly into the pipeby raising the scum to the edge of the scum inlet only by force of air.However, after heavy rain, as described above, there may be times whenlarge lumps of scum exist, becoming a possible obstacle in dischargingscum.

Furthermore, with conventional scum removing apparatus including thepatent apparatus, a part of the scum passes through the lower side ofthe pipe, namely a part of the scum travels around the lower side of thescum discharging mechanism and mixes into treated water, and therebycould lead to degradation of quality of the treated water.

As a result, the present invention is devised to resolve theseshortcomings. Objectives thereof are to provide a scum removingapparatus that, even when there are large lumps of scum exceeding 10 cmin diameter on the scum inlet side, can raise the large lumps of scum upto the edge of the scum inlet so as for them to flow smoothly into thepipe, and provide a scum removing apparatus that does not allowdegradation of treated water quality due to a part of the scum travelingaround the lower side of the scum discharging mechanism and mixing intothe treated water.

Means of Solving the Problems

To achieve the above-mentioned objectives, a scum removing apparatusaccording to the present invention is characterized in that it transfersgenerated scum on a current to a scum discharging mechanism side, andhas a part of a scum inlet of the scum discharging mechanism submergedin water at the time of discharging scum so as to remove the generatedscum. The scum removing apparatus comprises a spraying means on thescum-flowing wall surface side of wall surfaces forming the scum inletof the scum discharging mechanism, wherein the spraying means sprayspressured water upward along the wall surface on the scum-flowing sidefrom when a part of the scum inlet is submerged in water until the scumbegins to flow into the scum inlet.

Moreover, the present invention is characterized in that it furtherincludes a spraying means on the scum-flowing wall surface side of wallsurfaces forming the scum inlet of the scum discharging mechanism,wherein the spraying means sprays pressured water upward along the wallsurface on the scum-flowing side from when a part of the scum inlet issubmerged in water, and air is sprayed along the wall surface on thescum-flowing side for a predetermined period, until the scum begins toflow into the scum inlet.

Furthermore, the present invention is characterized in that it is alsoprovided with a spraying means on the basin wall side in the water nearthe basin wall further upstream than the position at which the scumdischarging mechanism is provided, and sprays air upward along the basinwall.

The present invention is further characterized in that spraying of airby the air spraying means is performed regularly.

In addition, the present invention is characterized in that it isprovided with a water spraying means, which is provided further upstreamthan the position at which the scum discharging mechanism is provided,and sprays water obliquely downward on the scum discharging mechanismside at the time of discharging scum to transfer the scum to the scumdischarging mechanism side by the spraying pressure of the water.

The present invention is further characterized in that the scumdischarging mechanism is a tubular scum discharging mechanism or atrough-type scum discharging mechanism.

The present invention is further characterized in that it includes ablocking board, which either extends downward for a predetermineddistance along the length of the bottom of a pipe of the tubular scumdischarging mechanism, or extends downward for a predetermined distancealong the length of the bottom of a trough of the trough-type scumdischarging mechanism.

The present invention is yet even further characterized in that sprayingof air by the spraying means is performed from small holes formed in thelower portion of an air supply pipe at constant predetermined intervalsalong the length thereof.

The present invention is yet even further characterized in that thespraying means includes small holes formed in the upper portion of anair supply pipe at predetermined intervals along the length thereof, andcovers are provided above the small holes at predetermined intervals.

The present invention is yet even further characterized in that sprayingof water by the water spraying means is performed from nozzles formedwith a flat and broadening outer shape, and structured so as to pump upwater from a middle layer in the basin.

Alternatively, to achieve the above-mentioned objectives, a scumremoving apparatus according to the present invention is characterizedin that it transfers generated scum on a current to a scum dischargingmechanism side, and has a part of a scum inlet of the scum dischargingmechanism submerged in water at the time of discharging scum so as toremove the generated scum. The scum discharging mechanism includeseither a tubular scum discharge mechanism, which includes a pipe havingan axial center direction parallel to the water surface and beingrotatable with the axis as a center and a slender opening in the axialcenter direction, and introduces scum into the pipe from the openingwhen a part of the opening is positioned below water, or a trough-typescum discharging mechanism, which introduces scum from a verticallymoving inflow floodgate into the trough when the upper part of theinflow floodgate is positioned below water. The scum dischargingmechanism further includes a blocking board, which either extendsdownward for a predetermined distance along the length of the bottom ofa pipe of the tubular scum discharging mechanism, or extends downwardfor a predetermined distance along the length of the bottom of a troughof the trough-type scum discharging mechanism.

EFFECTS OF INVENTION

Since the present invention includes a spraying means, which is providedon the scum-flowing wall surface side of wall surfaces forming a scuminlet of a scum discharging mechanism, and sprays pressured water upwardalong the wall surface on the scum-flowing side from when a part of thescum inlet is submerged in water until the scum begins to flow into thescum inlet, even when there are large lumps of scum exceeding 10 cm indiameter, the large lumps of scum may be raised to the edge of the scuminlet by the sprayed flow of water so as to flow smoothly into the scuminlet, thus allowing rapid discharge of scum.

Moreover, since the present invention includes a spraying means, whichis provided on the scum-flowing wall surface side of wall surfacesforming the scum inlet of the scum discharging mechanism, and sprayspressured water upward along the wall surface on the scum-flowing sidefrom when a part of the scum inlet is submerged in water, and air issprayed along the wall surface on the scum-flowing side for apredetermined period, until the scum begins to flow into the scum inlet,the scum strips away from wall surfaces by the air, and the strippedaway scum smoothly flows into the scum inlet by the sprayed water flow.

Furthermore, since the present invention is also provided with an airspraying means in the water near the basin wall further upstream thanthe position at which the scum discharging mechanism is provided, andsprays air upward along the basin wall, there is no more adherence ofscum to the basin walls due to the air, and thereby allowing efficienttransfer of the scum to the scum discharging mechanism side.

Yet even further, since the present invention performs spraying of airby the air spraying means regularly, there is no more adherence of scumto the basin walls due to the air, and thereby allowing efficienttransfer of the scum to the scum discharging mechanism side.

In addition, since the present invention is provided with a waterspraying means further upstream than the position at which the scumdischarging mechanism is provided, and sprays water obliquely downwardon the scum discharging mechanism side at the time of discharging scumto transfer the scum to the scum discharging mechanism side by thespraying pressure of the water, transfer of scum may be expedited.

Moreover, since the scum discharging mechanism is either a tubular scumdischarging mechanism or a trough-type scum discharging mechanismaccording to the present invention, the scum discharging mechanism maybe easily implemented, and the present invention may also be easilyimplemented into the existing scum discharging mechanism.

Furthermore, since the present invention further includes a blockingboard, which either extends downward for a predetermined distance alongthe length of the bottom of a pipe of the tubular scum dischargingmechanism, or extends downward for a predetermined distance along thelength of the bottom of a trough of the trough-type scum dischargingmechanism, traveling around of scum may be effectively prevented, anddegradation of treatment water quality may be prevented.

Yet even further, since the present invention performs spraying of airby the spraying means from small holes formed in the lower portion of anair supply pipe at constant predetermined intervals along the lengththereof, the small holes may be kept from clogging.

Yet even further, since the spraying means includes small holes formedin the upper portion of an air supply pipe at predetermined intervalsalong the length thereof, and covers are provided above the small holesat predetermined intervals, the present invention may effectivelyprevent the small holes from clogging.

Since spraying of water by the water spraying means is performed fromnozzles formed with a flat and broadening outer shape, and structured soas to pump up water from a middle layer in the basin, the presentinvention allows easy spraying of water, dispersion of pressured wateracross a wide area of scum, and effective transfer of the scum.

Furthermore, since the scum discharging mechanism further includes ablocking board, which either extends downward for a predetermineddistance along the length of the bottom of a pipe of the tubular scumdischarging mechanism, or extends downward for a predetermined distancealong the length of the bottom of a trough of the trough-type scumdischarging mechanism, the present invention may effectively preventtraveling around of scum, and prevent degradation of treatment waterquality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a part of a settling basin without a top coverto which is applied a scum removing apparatus according to an embodimentof the present invention;

FIG. 2 is a cross section cut along the line A-A of FIG. 1;

FIG. 3 is a cross section of a pipe in a state where a part of anopening of the pipe is positioned on the water surface;

FIG. 4 is a top view of the pipe shown in FIG. 3;

FIG. 5 is a cross section of a spraying means when small holes areformed at constant predetermined intervals along the length of thebottom of an air supply pipe;

FIG. 6 is a cross section of a spraying means when small holes areformed at constant predetermined intervals along the length of the topof an air supply pipe;

FIG. 7 is a perspective view of a nozzle;

FIG. 8 is a block diagram of a controller;

FIG. 9 is a cross section of a pipe in a state where a part of anopening of the pipe is positioned below water, and when there are nolarge lumps of scum exceeding 10 cm in diameter in the scum;

FIG. 10 is a cross section of a pipe in a state where a part of anopening of the pipe is positioned below water, and when there are largelumps of scum exceeding 10 cm in diameter in the scum;

FIGS. 11A to 11C are time charts showing control action;

FIG. 12 is an explanatory drawing for when a trough-type scumdischarging mechanism is implemented in the scum removing apparatusaccording to the present invention; and

FIG. 13 is an explanatory drawing for when another form of trough-typescum discharging mechanism is implemented in the scum removing apparatusaccording to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is described in detail forthwith based on attacheddrawings.

FIG. 1 is a top view of a part of a settling basin 1 at a sewage plantto which is applied a scum removing apparatus according to anembodiment, and FIG. 2 is a cross section cut along the line A-A ofFIG. 1. FIG. 1 is a view without a top cover 2 shown in FIG. 2. Notethat the nature of this settling basin 1 is no object as long as it is atank of water in which scum generates, such as a primary sedimentationtank, a final sedimentation tank, or a conduit for them at the sewageplant.

In FIG. 1 and FIG. 2, a conduit (not shown in the drawings) for rawwater to flow in is provided on the right side, and an overflow trough 3for extracting treated water is provided on the downstream side thereof.Accordingly, this illustrated example is structured such that waterflows from left to right as indicated by arrow a. Moreover, thissettling basin 1 is structured such that the water channel width becomesnarrower on the downstream side (on the right side in the illustratedexample) than on the upstream side. Furthermore, scum generating on thetop surface of the settling basin 1 is omitted from FIG. 1 and FIG. 2 inorder to avoid complication in the drawings. Note that this scum isindicated by symbols “S and S′” in FIGS. 9 and 10 to be described later.

In the drawings, 10 denotes a tubular scum discharging mechanismprovided on the downstream side of the settling basin 1, 20 denotes aspraying means according to the present invention, 30 denotes an airspraying means according to the present invention, and 40 denotes awater spraying means according to the present invention. First, thetubular scum discharging mechanism 10, the spraying means 20, and theair spraying means 30 will be described using FIGS. 3 and 4, togetherwith FIGS. 1 and 2.

The tubular scum discharging mechanism 10 is provided, in which a pipe11 has a predetermined thickness such that the center of axle roughlycorresponds with the water surface, and crosses over the settling basin1. An end side (upper end side in FIG. 1) of this pipe 11 is positionedwithin a sump pit 12 provided on a side wall 1 a (upper side wall inFIG. 1) of the settling basin 1, and a rotating mechanism 13, which isconstituted by a motor and the like for rotating the pipe 11 back andforth as indicated by arrow b in FIG. 1, is provided on the other endside of the pipe 11. In addition, the pipe 11 has a slender opening 14in the axial center direction corresponding to the scum inlet of thepresent invention. In the illustrated example, this opening 14 is formedwith length equal to the width of the settling basin 1, and width of theopening corresponds to an approximate 90 degree angle centered aroundthe center location of the pipe 11.

The rotating mechanism 13 is structured, as shown in FIGS. 2 and 3, torotate such that the opening 14 of the pipe 11 is positioned on thewater surface when the pipe is not discharging scum. As shown in FIGS. 9and 10, the rotating mechanism 13 can rotate a predetermined angle(predetermined angle in the counterclockwise direction in the example ofFIGS. 9 and 10) such that a part of the opening 14 of the pip 11 ispositioned below water at the time of discharging scum, which will bedescribed later.

In FIG. 3, 15 denotes a blocking board provided at the bottom of thepipe 11. The blocking board extends, for example, approximately 30 cmfrom the bottom of the pipe 11 and also extends in the axial centerdirection of the pipe 11 for a predetermined distance. When the blockingboard 15 is provided to the pipe 11 in this manner, scum flowingdownstream from the lower part of the pipe 11 may be effectivelyprevented, and scum mixing into treated water may also be prevented.Note that while the longer this blocking board 15 extends downward, thebetter the effect of preventing scum from mixing into the treated water,if it is too long, it adversely affects the sedimentation effect of thesettling basin, and thus the aforementioned approximate 30 cm isfavorable.

The spraying means 20 includes an air spray pipe 21 made up of asynthetic resin pipe and the like for spraying compressed air, and apressured water spray pipe 22 made up of a synthetic resin pipe and thelike for spraying pressured water. Axial center direction of these pipes21 and 22 is parallel to that of the pipe 11, and is provided via asupport member 23 on the side wall (left side wall of the pipe 11 in theillustrated example) on the scum-flowing side of the pipe 11. Thesepipes 21 and 22 are positioned at least below the generating scum. Ofthese pipes 21 and 22, the air spray pipe 21 is provided closer to thepipe 11 than the pressured water spray pipe 22.

Note that the pressured water spray pipe 22 may alternatively beprovided closer to the pipe 11 than the air spray pipe 21. Moreover,while these pipes 21 and 22 have been attached to the pipe 11, both endsides of these pipes 21 and 22 may be fixed and attached to basin walls1 a and 1 b, respectively, without attaching them to the pipe 11.However, attaching them to the pipe 11 as illustrated is easier toattach and provides a simpler structure.

As shown enlarged in FIG. 5, the air spray pipe 21 includes multiplesmall holes 24 formed in the lower portion at constant predeterminedintervals along the length thereof. Compressed air is sprayed downwardfrom these small holes 24 and is then aimed upward due to buoyancy (Seearrows c in FIG. 5.) Moreover, as shown enlarged in FIG. 5, thepressured water spray pipe 22 includes multiple small holes 25 formed inthe upper portion at constant predetermined intervals along the lengththereof. Pressured water is delivered upward from these small holes 25(See Arrow D in FIG. 5.)

FIG. 6 shows another example of the air spray pipe 21. The small holes24 provided in the air spray pipe 21 are formed in the upper portion atconstant predetermined intervals along the length thereof, and covers 26are provided above the small holes 24, respectively, at constantpredetermined intervals. As a result, air bypasses the covers 26 andrises as indicated by arrows e in FIG. 6. When the covers 26 areprovided above the small holes 24, respectively, in this manner, even ifthe small holes 24 are provided turned upward, blockage of the smallholes 24 by scum may be effectively prevented as in the case when thesmall holes 24 are provided turned down, as shown in FIG. 5. Note thateven in FIG. 6, the pressured water spray pipe 22 is structured as inFIG. 5, and pressured water may thus by sprayed upward from the smallholes 25 (See arrow f in FIG. 6.)

The air spraying means 30 includes aeration pipes 31 a and 31 b attachedto both side walls 1 a and 1 b of the settling basin 1, respectively.These aeration pipes 31 a and 31 b are provided on the side walls 1 aand 1 b, respectively, via fixing brackets not shown in the drawingsapproximately 10 cm below the water surface of the settling basin 1, andlike the air spray pipe 21, are structured with multiple small holesformed at constant predetermined intervals along the length of the pipesmade of synthetic resin and the like.

In FIG. 1, 51 a denotes an air supply pipe including an automaticopening and closing valve V₁ arranged midway for supplying compressedair from a compressed air supply source, which is not shown in theillustration, to the air spray pipe 21, and 51 b denotes an air supplypipe for supplying compressed air from a compressed air supply source,which is not shown in the illustration, to the aeration pipes 31 a and31 b. When the settling basin 1 is provided in a sewage plant, apart ofcompressed air used in an aerating tank may be used as the compressedair supply source. Needless to say that a compressor may also beinstalled to obtain compressed air. Note that in the illustratedexample, since the air spray pipe 21 provided on the pipe 11 moves asthe pipe 11 rotates, a flexible tube not shown in the drawing isprovided at the connecting part of the air supply pipe 51 a and the airspray pipe 21.

The water spraying means 40 includes a header pipe 41, which ispositioned (position a little more upstream from the portion where thewidth of the settling basin 1 narrows in the illustrated example) apredetermined distance further upstream than the tubular scumdischarging mechanism 10, and extends in a direction orthogonal to thewater flow of the settling basin 1. Moreover, the header pipe 41 hasmultiple nozzles 42 provided at constant predetermined intervals alongthe length thereof. Each of the nozzles 42 is structured so as to spraypressured water toward the tubular scum discharging mechanism 10, namelytoward downstream of the settling basin 1.

As shown in FIG. 7, each of the nozzles 42 is formed with a flat andbroadening outer shape, and is structured so as to spray membranouspressured water from respective slits 42 a formed in broadening endsurfaces thereof, respectively. As a result, pressured water may bedispersed from each of the nozzles 42 across a wide area of scum, andthe scum may be efficiently moved toward the tubular scum dischargingmechanism 10.

In FIG. 1, 52 a denotes a pressured water supply pipe including anautomatic opening and closing valve V₂ arranged midway for supplyingpressured water pumped up by a pump P from a middle layer furtherdownstream than the installed position of the tubular scum dischargingmechanism 10 to the pressured water spray pipe 22, and 52 b denotes apressured water supply pipe for supplying pressured water pumped up bythe pump P to the header pipe 41.

In FIG. 2, 60 denotes a sludge collecting mechanism of the settlingbasin 1, and is structured with collective plates 62 provided atconstant predetermined intervals on an endless chain conveyer 61. Thissludge collecting mechanism 60 is structured so as to discharge to a pitnot shown in the drawing, sludge (sediment) piled up at the bottom ofthe settling basin 1 on the forward moving side of the chain conveyer61, and so as to transfer the scum to the tubular scum dischargingmechanism 10 on the backward moving side of the chain conveyer 61.

FIG. 8 is a block diagram of a controller 70 constituted by a programcontroller for managing control of driving the scum removing apparatus.The controller 70 includes a control unit 71 mainly constituted by aCPU. This control unit 71 is connected to a setting device 72, whichsets rotating times of the pipe 11 and opening and closing times of theautomatic opening and closing valves V₁ and V₂, and selects and sets forthe scum removing apparatus normal mode for times other than duringheavy rain, heavy rain mode for during heavy rain (includes during heavyrain and a predetermined period thereafter), and other various modes; apipe rotation driver 73, which controls driving of a motor of therotating mechanism 13 to drive the rotation of the pipe 11; a pumpdriver 74, which controls driving of the pump P; and a valve driver 75,which controls driving of the automatic opening and closing valves V₁and V₂.

The scum discharging operations of the scum removing apparatus with theaforementioned configuration will be described using the explanatorydrawings FIGS. 9 and 10 and the time charts FIGS. 11A, 11B, and 11C.FIG. 9 and FIG. 10 respectively show a state where it is time fordischarging scum, the pipe 11 rotates a predetermined angle from theposition of FIG. 3 in the anticlockwise direction so that edge (rim) 14a on the upstream side (left side in the illustrated examples) of theopening 14 is positioned below water at a predetermined depth. Moreover,FIG. 9 shows a normal state other than during heavy rain wheregenerating scum S has a thickness of 10 cm or less. On the other hand,FIG. 10 shows a state during heavy rain where the generating scum Sincludes large lumps of scum S′ of thickness (diameter) exceeding 10 cm.Furthermore, FIG. 11A shows a time chart for normal mode not duringheavy rain, and FIGS. 11B and 11C show time charts for heavy rain mode.

Assume it is not during heavy rain now. In this case, the scum removingapparatus is set to normal mode via the setting device 72. Here, untilit becomes time to discharge the scum S, the opening 14 of the pipe 11of the tubular scum discharging mechanism 10 is positioned on the watersurface, as shown in FIG. 3. As a result, since the scum S is notdischarged from the pipe 11, it gradually accumulates plate-like on theupstream side of the pipe 11. Moreover, compressed air is regularlysupplied from the aeration pipes 31 a and 31 b to spray air bubblesalong both of the side walls 1 a and 1 b of the settling basin 1, andaccordingly, a state where no scum S is attached (adhered) to both ofthe side walls 1 a and 1 b, namely lumps of plate-like scum S are allfloating on the water surface is maintained.

Next, when it becomes time to discharge the scum S, for example, whenone week elapses from the previous scum discharge time, as shown in FIG.11A, the pipe 11 rotates by the rotating mechanism 13 for apredetermined duration (for example, 10 minutes) so that a part of theopening 14 is submerged in water (See FIG. 9.) When a part of theopening 14 of the pipe 11 is submerged in water, the water sprayingmeans 40 also begins driving at the same time to spray pressured waterfrom the nozzles 42 on the scum S. As a result, moving the scum S to thetubular scum discharging mechanism 10 is expedited by locomotive facultyimparted from the pressured water in addition to the scum movement dueto water flow (see arrow a) in the settling basin 1.

Moreover, the automatic opening and closing valve V₁ is opened for apredetermined duration (for example, 30 seconds) at the same time that apart of the opening 14 of the pipe 11 is submerged in water so as tospray air from the air spray pipe 21. Due to this sprayed air, the scumS in the vicinity of the opening 14 of the pipe 11 is raised by airbubbles, and the raised scum S passes over the end 14 a of the opening14 and is lead smoothly into the pipe 11. Once the scum S has enteredthe pipe 11 from the opening 14, all of subsequent scum S is leadsmoothly into the pipe 11. It is sufficient for introduction of the scumS into the opening 14 by spraying of air to be carried out for a veryshort time of approximately 30 seconds since scum will continue to belead smoothly into the pipe 11 by the flowing force of the scum Sthereafter. Since air needs to be sprayed for only a short period assuch, scum discharge may be possible at a lower cost.

Furthermore, since the scum S is completely separated from both of theside walls 1 a and 1 b due to air bubbles from the aeration pipes 31 aand 31 b in this scum discharging process, movement of all of the scumis carried out smoothly so that all of the scum moves rapidly into thepipe 11 from the opening 14.

Therefore, with this scum removing apparatus, an exceptional result ofallowing amount of water taken into the pipe 11 for discharging all ofthe scum S to be reduced to 1/20 to 1/30 when all of the scum S isdischarged by driving only the water spraying means 40 may be attained.

The scum S taken into the pipe 11 is lead into the sump pit 12,delivered to a scum processing unit, which is not shown in the drawing,including a hydro-extractor or the like, and then processed. Sinceamount of water included in the scum S is very little, processing costmay be lowered even with this scum processing unit.

After the scum S is taken into the pipe 11 and removed from the watersurface of the settling basin 1, the pipe 11 is rotated via the rotatingmechanism 13 to the original position, that is, the opening 14 of thepipe 11 is positioned on the water surface (See FIG. 3), and driving ofthe water spraying means 30 is stopped, thereby completing the sequenceof scum discharging operations.

Next, the case of during heavy rain will be described. In this case, thescum removing apparatus is set to heavy rain mode via the setting device72. Here, the opening 14 of the pipe 11 is positioned on the watersurface until it is time for discharging the scum S, and the scum S isgradually accumulated plate-like on the upstream side of the pipe 11since it is not discharged from the pipe 11. The scum S includes largelumps of scum S′ exceeding 10 cm in diameter that have stripped awayfrom sewage pipe inner surfaces and the like due to water flow and waterpressure during heavy rain. Note that even in this case, compressed airis regularly supplied from the aeration pipes 31 a and 31 b to spray airbubbles along both of the side walls 1 a and 1 b of the settling basin1, and accordingly, a state where no scum S is attached (adhered) toeither of the side walls 1 a and 1 b, namely lumps of platy scum S areall floating on the water surface is maintained.

When it becomes time to discharge the scum S, for example, as shown inFIG. 11B, the pipe 11 rotates by the rotating mechanism 13 for apredetermined duration (for example, 10 minutes) so that a part of theopening 14 is submerged in water (See FIG. 10.) When a part of theopening 14 of the pipe 11 is submerged in water, the water sprayingmeans 40 also begins driving at the same time to spray pressured waterfrom the nozzles 42 on the scum S. As a result, moving the scum S and S′to the tubular scum discharging mechanism 10 is expedited by locomotivefaculty imparted from the pressured water in addition to the scummovement due to water flow (see arrow a) in the settling basin 1.

Moreover, the automatic opening and closing valve V₂ is opened for apredetermined duration (for example, 30 seconds) at the same time that apart of the opening 14 of the pipe 11 is submerged in water so as tospray pressured water from the pressured water spray pipe 22. Due tothis sprayed pressured water, the scum S′ in the vicinity of the opening14 of the pipe 11 is raised by the sprayed flow of water, and the scumS′ passes over the end 14 a of the opening 14 and is lead smoothly intothe pipe 11 (See arrow h in FIG. 10.) Once the scum S′ has entered thepipe 11 from the opening 14, all of subsequent scum S and S′ is leadsmoothly into the pipe 11. It is sufficient for introduction of the scumS into the opening 14 by spraying of pressured water to be carried outfor a very short time of approximately 30 seconds since scum willcontinue to be lead smoothly into the pipe 11 by the flowing force ofthe scum S thereafter. Since pressured water needs to be sprayed foronly a short period as such, scum discharge may be possible at a lowercost.

Furthermore, since the scum S and S′ is completely away from either ofthe side walls 1 a and 1 b due to air bubbles from the aeration pipes 31a and 31 b in this scum discharging process, moving all of the scum iscarried out smoothly so as to rapidly move into the pipe 11 from theopening 14.

The scum discharging operation of the time chart shown in FIG. 11C hasan additional operation of releasing air from the air spray pipe 21 ofthe scum discharging operation shown in the aforementioned FIG. 11B.More specifically, in this air emitting operation, the automatic openingand closing valve V₁ is opened for a predetermined duration (forexample, 10 seconds) at the same time that a part of the opening 14 ofthe pipe 11 is submerged in water so as to spray air from the air spraypipe 21. After the scum S and S′ adhered to the pipe 11 is effectivelystripped away from the pipe 11 by the sprayed air, the automatic openingand closing valve V₂ is opened for a predetermined duration (forexample, 30 seconds) so as to spray pressured water from the pressuredwater spray pipe 22. Due to this sprayed pressured water, the scum S andS′ in the vicinity of the opening 14 of the pipe 11 is raised by thesprayed flow of water, and the scum S and S′ passes over the end 14 a ofthe opening 14 and is lead smoothly into the pipe 11.

As such, even if the scum S generating in the settling basin 1 includeslarge lumps of scum S′ exceeding 10 cm in thickness (diameter), since itis lead smoothly into the pipe 11 by the water flow sprayed from thepressured water spray pipe 22, even the conventional scum removingapparatus, which discharges scum by driving only the conventional waterspraying means, may attain an exceptional result of reducing the amountof discharged water accompanying scum discharge to 1/20 to 1/30.

FIG. 12 and FIG. 13 show the scum removing apparatus according to thepresent invention implemented by a trough-type scum dischargingmechanism. FIG. 12 is structured with a vertically moving inflowfloodgate 81 provided on the upstream side (on the left side in FIG. 12)of a trough 80, which is for taking in scum. The spraying means 20,which includes the air spray pipe 21 and the pressured water spray pipe22, is provided on the upstream side of this inflow floodgate 81 via thesupporting member 23. Moreover, the same blocking board 15 provided tothe aforementioned pipe 11 is provided on the bottom of this trough 80.

Meanwhile, FIG. 13 shows the scum discharging mechanism of the scumremoving apparatus according to the present invention implemented byanother form of trough-type scum discharging mechanism. This trough-typescum discharging mechanism is provided with a side wall upper portion91, which is on the upstream side of a trough 90 for taking in scum,freely rotatable via a hinge 92. It is structured such that when scum istaken in, it is rotated to submerge the upper end of the side wall upperportion 91 in the water so as to bring the scum into the trough 90. Inthe same way as with the aforementioned trough 80, the spraying means 20is also provided on the upstream side of the trough 90, and the samestopping board 15 as with the trough 80 is provided on the bottom ofthis trough 90.

In the case of using such trough-type scum discharging mechanisms forthe scum discharging mechanism, the pipe rotation driver 73 of thecontrol unit 70 is a driver for either vertically moving the inflowfloodgate 81 or rotating the side wall upper portion 91.

Experimental Example

A scum discharging experiment has been conducted in an actual settlingbasin of a sewage plant during heavy rain. A tubular scum dischargingmechanism including the spraying means 20 shown in FIG. 6 is installedin the settling basin of this experiment. Large lumps of scum exceeding10 cm in thickness (diameter) existed on the upstream side of thetubular scum discharging mechanism during heavy rain. When pressuredwater was sprayed for 30 seconds from a pressured water spray pipe ofthe spraying means at the time of discharging scum, large lumps of scumcould easily be raised to the position of the edge of the pipe opening,and discharging the scum thereafter could be performed smoothly. On theother hand, when only air is sprayed from the spraying means, largelumps of scum could not be raised to the position of the edge of thepipe opening, and there was trouble in discharging the scum thereafter.

INDUSTRIAL APPLICABILITY

Not only is the scum removing apparatus according to the presentinvention used in sewage plants, but it is also applicable in watertanks generating scum in wastewater processing facilities for varioustypes of industrial wastewater and the like. Moreover, it is alsoapplicable when making valuable resources surface and separating them ina food factory, chemical factory, etc. Consequently, ‘water’ with thepresent invention means not only sewage water or wastewater but alsovarious liquids.

1. A scum removing apparatus, which transfers generated scum on acurrent to a scum discharging mechanism side, and has a part of a scuminlet of the scum discharging mechanism submerged in water at the timeof discharging scum so as to remove the generated scum; said scumremoving apparatus comprising a spraying means on the scum-flowing wallsurface side of wall surfaces forming the scum inlet of the scumdischarging mechanism, wherein the spraying means sprays pressured waterupward along the wall surface on the scum-flowing side from when a partof the scum inlet is submerged in water until the scum begins to flowinto the scum inlet.
 2. A scum removing apparatus, which transfersgenerated scum on a current to a scum discharging mechanism side, andhas a part of a scum inlet of the scum discharging mechanism submergedin water at the time of discharging scum so as to remove the generatedscum; said scum removing apparatus comprising a spraying means on thescum-flowing wall surface side of wall surfaces forming the scum inletof the scum discharging mechanism, wherein the spraying means sprayspressured water upward along the wall surface on the scum-flowing sidefrom when a part of the scum inlet is submerged in water, and air issprayed along the wall surface on the scum-flowing side for apredetermined period, until the scum begins to flow into the scum inlet.3. The scum removing apparatus according to claim 2, further comprisingan air spraying means, which is provided in the water near a basin wallfurther upstream than the position at which the scum dischargingmechanism is provided, wherein the air spraying means sprays air upwardalong the basin wall.
 4. The scum removing apparatus according to claim3, wherein spraying of air by said air spraying means is performedregularly.
 5. The scum removing apparatus according to claim 4, furthercomprising a water spraying means, which is provided further upstreamthan the position at which the scum discharging mechanism is provided,wherein the water spraying means sprays water obliquely downward on thescum discharging mechanism side at the time of discharging scum totransfer the scum to the scum discharging mechanism side by the sprayingpressure of the water.
 6. The scum removing apparatus according to claim5, wherein said scum discharging mechanism is a tubular scum dischargingmechanism, which comprises a pipe having an axial center directionparallel to the water surface, including a slender opening in the axialcenter direction and being rotatable with the axis as a center, andintroduces scum into the pipe from the opening when a part of theopening is positioned below water, or said scum discharging mechanism isa trough-type scum discharging mechanism, which introduces scum from avertically moving inflow floodgate into the trough when the upper partof the inflow floodgate is positioned below water.
 7. The scum removingapparatus according to claim 6, further comprising a blocking board,which either extends downward for a predetermined distance along thelength of the bottom of a pipe of said tubular scum dischargingmechanism, or extends downward for a predetermined distance along thelength of the bottom of a trough of said trough-type scum dischargingmechanism.
 8. The scum removing apparatus according to claim 7, whereinspraying of air by said spraying means is performed from small holesformed in the lower portion of an air supply pipe at constantpredetermined intervals along the length thereof.
 9. The scum removingapparatus according to claim 7, wherein said spraying means comprisessmall holes formed in the upper portion of an air supply pipe atconstant predetermined intervals along the length thereof, and coversare provided above the small holes at constant predetermined intervals.10. The scum removing apparatus according to claim 9, wherein sprayingof water by said water spraying means is performed from nozzles formedwith a flat and broadening outer shape, and structured so as to pump upwater from a middle layer in the basin.
 11. A scum removing apparatus,which transfers generated scum on a current to a scum dischargingmechanism side, and has a part of a scum inlet of the scum dischargingmechanism submerged in water at the time of discharging scum so as toremove the generated scum; said scum discharging mechanism compriseseither a tubular scum discharge mechanism, which includes a pipe havingan axial center direction parallel to the water surface and beingrotatable with the axis as a center and a slender opening in the axialcenter direction, and introduces scum into the pipe from the openingwhen a part of the opening is positioned below water, or a trough-typescum discharging mechanism, which introduces scum from a verticallymoving inflow floodgate into the trough when the upper part of theinflow floodgate is positioned below water, wherein the scum dischargingmechanism further comprises a blocking board, which either extendsdownward for a predetermined distance along the length of the bottom ofa pipe of the tubular scum discharging mechanism, or extends downwardfor a predetermined distance along the length of the bottom of a troughof the trough-type scum discharging mechanism.
 12. The scum removingapparatus according to claim 1, further comprising an air sprayingmeans, which is provided in the water near a basin wall further upstreamthan the position at which the scum discharging mechanism is provided,wherein the air spraying means sprays air upward along the basin wall.13. The scum removing apparatus according to claim 12, wherein sprayingof air by said air spraying means is performed regularly.
 14. The scumremoving apparatus according to claim 13, further comprising a waterspraying means, which is provided further upstream than the position atwhich the scum discharging mechanism is provided, wherein the waterspraying means sprays water obliquely downward on the scum dischargingmechanism side at the time of discharging scum to transfer the scum tothe scum discharging mechanism side by the spraying pressure of thewater.
 15. The scum removing apparatus according to claim 14, whereinsaid scum discharging mechanism is a tubular scum discharging mechanism,which comprises a pipe having an axial center direction parallel to thewater surface, including a slender opening in the axial center directionand being rotatable with the axis as a center, and introduces scum intothe pipe from the opening when a part of the opening is positioned belowwater, or said scum discharging mechanism is a trough-type scumdischarging mechanism, which introduces scum from a vertically movinginflow floodgate into the trough when the upper part of the inflowfloodgate is positioned below water.
 16. The scum removing apparatusaccording to claim 15, further comprising a blocking board, which eitherextends downward for a predetermined distance along the length of thebottom of a pipe of said tubular scum discharging mechanism, or extendsdownward for a predetermined distance along the length of the bottom ofa trough of said trough-type scum discharging mechanism.
 17. The scumremoving apparatus according to claim 16, wherein spraying of water bysaid water spraying means is performed from nozzles formed with a flatand broadening outer shape, and structured so as to pump up water from amiddle layer in the basin.